The instant invention relates to temporary corrosion resistant coatings and films upon metal substrates, e.g., metal tools and dies. The temporary coatings and films will not adversely chemically alter the surface of the underlying substrate. The coatings/films can comprise a mixture of at least one of an acrylic, glycerin, water, an oil, e.g., vegetable such as canola, linseed and castor, synthetic oils such as polyalphaolefin (PAO), polybutenes, polyglycol, silicone, and phosphate esters; naturally occurring oils such as mineral oil, mixtures thereof, among others; silica, at least one silicate, surfactants and optionally one or more buffering materials and waxes.
The corrosion of steel and other metal containing products continues to be a serious technical problem which has profound effects on the economy. Corrosion causes loss of natural resources, and deteriorates key infrastructure such as roads and buildings. It also causes premature replacement of equipment and parts in industrial facilities, boats and other marine vehicles, automobiles, aircraft, among a wide range of metallic components.
Current industry standards for corrosion prevention center around the use of barrier coatings, sacrificial coatings, alloys containing heavy metals such as chromium, nickel, lead, cadmium, copper, mercury, barium, among other heavy metals. Conventional coatings can also include volatile organic compounds (V.O.C.s) or solvents such those disclosed in U.S. Pat. No. 4,631,083 (Dec. 23, 1986 to Christhilf); hereby incorporated by reference. The introduction of these materials into the environment, however, can lead to serious health consequences as well as substantial costs to contain or separate the materials or clean up environmental contamination. Damage associated with corrosion, accordingly, is a continuing problem and better systems for preventing corrosion are still needed.
In many applications, metal articles which are used as tool steels, particularly in steel cutting tools, injection molding, e.g., plastic shaping, dies, e.g., extrusion dies, molds, e.g., for shaping polymers, glass, nylon, among other materials; become corroded while being stored. Conventional corrosion protection methods adversely impact the performance of the underlying metal article and suffer from undesirable environmental characteristics.
The instant invention solves problems associated with conventional methods for protecting metal containing surfaces by providing a temporary metal coating/film which protects the metal surface from corrosion, and is cost-effective, typically non-toxic and non-flammable. By temporary it is meant that in typically end-uses the coating protects the metal surface for a period of less than about 6 months, or longer depending upon the environment to which the metal is exposed. The inventive coating/film can also obviate using heavy metals such as chromium for corrosion protection. The inventive coating, however, can enhance the corrosion resistance of chrome-containing alloys.
The inventive coating/film comprises or consists essentially of at least one member from the group of a carrier such an acrylic, glycerin, water, an oil, e.g., vegetable such as canola, linseed and castor, synthetic oils such as polyalphaolefin (PAO), polybutenes, polyglycols, silicone and phosphate esters, naturally occurring oils such as mineral oil, mixtures thereof, among others; silica, at least one silicate, surfactants and an optional buffering material and optionally at least one wax. Suitable acrylics for the carrier include polymers formed from acrylic acid, methacrylic acid and their esters, e.g., methyl-methacrylate, and combinations thereof. While the inventive coating/film is desirable in that solvents, e.g., (V.O.C.s), are unnecessary, the presence of a suitable solvent does not adversely effect the utility of the inventive coating/film and if desired hydrocarbons can be employed as propellants to apply the inventive composition. The inventive coating can be applied in any expedient manner such as painting, dipping, spraying, e.g., an aerosol spray, among other application methods. If desired, the coating/film can be removed from the metal surface by washing with a suitable surfactant, or dry-wiped in the case of a self-supporting film by being stripped from the underlying surface, e.g, the self-supporting film may be removed by a plastic molding process.
In general, the carrier provides a coating or layer to cover the surface to be protected; provides a dispersion medium for the corrosion inhibitor, and provides a physical barrier to inhibit corrosive materials from reaching the surface. The suitable carrier materials include materials which yield self-supporting films, such as acrylic-based carriers and oxidizable carriers and those which do not produce self-supporting films as in the case of many oil-based carriers. By self-supporting film, it is meant that the carrier, after drying or curing, produces a material that can be stripped or peeled from the substrate as a film or as sections of film.
In one aspect of the invention, the inventive coating/film forming composition comprises an acrylic based material. When employing an acrylic based composition, a strippable self-supporting coating/film can form upon the surface of the underlying metal. That is, the acrylic based composition can be applied upon a metal surface, allowed to dry (or cure), and removed when desired by peeling or stripping the self-supporting film from the surface of the metal.
In another aspect of the invention, the inventive coating/film forming composition comprises a composition based upon an oil such as vegetable, canola, linseed, mineral, PAO, mixtures thereof, among others. The oil can function as a vehicle for delivering at least one of silica and/or silicate, among other compounds, as well as a physical barrier for protecting the underlying metal surface, e.g., from humidity.
In a further aspect of the invention, the inventive coating/film forming composition comprises an oxidizable carrier. By xe2x80x9coxidizablexe2x80x9d carrier, it is meant that a carrier such as a naturally occurring oil is crosslinked and converted after being applied upon the metal surface. For example, in the case of a cedar or linseed oil carrier, the carrier can become at least partially cross-linked thereby forming a coating/film which is relatively dense and self-supporting. In some cases, at least a portion of the coating/film underlying the oxidized surface remains in an uncured state. Depending upon the characteristics of the oxidizable carrier and the surrounding environment, such a carrier can provide improved physical resistance to corrosion such as water repellence (in addition to the affects of a silica or silicate containing compound).
The subject matter of the instant invention is related to copending and commonly assigned Non-Provisional U.S. patent application Ser. Nos. 09/016,853 (Attorney Docket No. EL001RH-8) filed on even date herewith, 08/850,323 and 08/850,586 (Attorney Docket Nos. EL001RH-6 and EL001RH-7) filed on May 2, 1997; and Ser. Nos. 08/791,336 (Attorney Docket No. EL001RH-5) and 08/791,337 (Attorney Docket No. EL001RH-4) filed on Jan. 31, 1997 in the names of Robert L. Heimann et al., as a continuation in part of Ser. No. 08/634,215 (Attorney Docket No. EL001RH-3 filed on Apr. 18, 1996) in the names of Robert L. Heimann et al., and entitled xe2x80x9cCorrosion Resistant Buffer System for Metal Productsxe2x80x9d, which is a continuation in part of Non-Provisional U.S patent application Ser. No. 08/476,271 (Attorney Docket No. EL001RH-2 filed on Jun. 7, 1995) in the names of Heimann et al., and corresponding to WIPO Patent Application Publication No. WO 96/12770, which in turn is a continuation in part of Non-Provisional U.S. patent application Ser. No. 08/327,438 (Attorney Docket No. EL001RH-1 filed on Oct. 21, 1994), now allowed.
The disclosure of the previously identified patent applications and publication is hereby incorporated by reference.